Autonomous registration is an overhead mobile radiotelephone locating function used in a cellular system to identify the mobile radiotelephones covered for service within a particular local cellular service system, e.g. a cellular geographic service area. Autonomous registration may be time based and/or geographic based. In time based autonomous registration, the registration of a mobile radiotelephone is in response to the passage of a time interval as defined by a clock. Geographic based autonomous registration is based on the location of the mobile radiotelephone; e.g. a roamer (e.g., a mobile radiotelephone away from its home territory) autonomously registers when it enters the territory of a new cellular system. Detailed particulars concerning the requirements and operation of autonomous registration in a cellular mobile radiotelephone system may be found in the published standard EIA-553.
Each mobile radiotelephone, when not engaged in making a call, continuously listens to a set-up channel with control information and sends overhead messages via a reverse signalling channel. System identification code signals generated by the base stations of the cellular system identify the presently serving cellular system to the mobile radiotelephone. These identification code signals include time stamp signals which are periodically incremented at some specific rate. In a time response autonomous registration each mobile radiotelephone compares a timed identification stamp or marker (REGID) received from the base station with a stored value of its next registration (NXTREG) which was calculated from parameters received in a previous overhead signal transmission.
If a mobile radiotelephone begins to lose reception of its present identifying code signal it searches for a new better quality identification code signal. If the new identification code signal indicates that the mobile radiotelephone system is in a new cellular service area, the mobile radio telephone automatically registers with the new base station.
In registering, the mobile radiotelephones send their serial number and related information to the local cellular service system over a reverse radio channel dedicated to transmitting overhead messages of this type. This reverse channel is normally used for a variety of purposes, e.g. control messages sent for the purpose of originating phone calls, in addition to the registration of mobile radiotelephones with the base station.
Since the transmission capacity of the reverse channel is limited, the need to process a large number of autonomous registrations will fill the reverse channel to capacity and block or severely limit transmissions of the other overhead messages that operate to originate calls and perform other support services.